It is known that compounds having a muscarinic receptor antagonizing effect induce bronchodilation, gastrointestinal motility inhibition, gastric acid secretion reduction, dry mouth, mydriasis, tachycardia, as well as urinary bladder contraction inhibition.
Between 1983 and 1993, continuous advances were produced in the knowledge of muscarinic receptor pharmacology. During this period, a total of five human genes codifying muscarinic receptor subtypes (m1, m2, m3, m4 and m5) were cloned and expressed, which encoded five functional receptors (M1, M2, M3, M4 and M5). Although M5 is not completely characterized, it is already considered a functional receptor according to NC-IUPHAR Guidelines (M. P. Caulfield et al.; Pharmacol. Rev. 1998, 50, 279–290).
The M1 receptor is a postsynaptic neuronal receptor mainly located in brain and peripheral parasympathetic glands. In smooth cardiac muscle there is a major population of M2 receptors. The M3 receptor is predominantly located in glandular exocrine tissues such as salivary glands. The M4 receptor is mainly present in cerebral cortex, striatum and some peripheral locations in specific species. In the smooth muscle of intestinal tract, bladder and bronchus, M2 and M3 receptors coexist. Nevertheless, functional information commonly accepted indicates that the M3 receptor is the responsible for the contractile effect of the endogenous neurotransmitter in the latter three tissues. Thus, it seems interesting to obtain M3 receptor selective antagonists to avoid the adverse effects due to blockade of other muscarinic receptors. At present, oxybutynin (Nippon Shinyaku), and tolterodine (Pharmacia) among others are commercially available compounds, both showing reduced selectivity for M2 and M3 receptors. However, darifenacin (Pfizer), and YM-905 (Yamanouchi), both in development phase, exhibit M3 antagonist activity without any significant affinity towards the M2 receptor.

The following are some patent applications claiming compounds with carbamic structures as selective M3 receptor antagonists: JP 04/95071-A, WO 95/06635-A, EP 747355-A and EP 801067-A. All of them describe carbamates different to those described in the present invention, and the last one describes the structurally nearest to the hereby claimed.
Therefore, it is understood that there is a big interest in providing new therapeutic agents that are selective M3 receptor antagonists.